Zinc alloy and method of making same



1 United States Patent 3,254,993 Patented June 7, 1966 No Drawing. Filed Mar. 18, 1963, Ser. No. 266,039 15 Claims. (Cl. 75-135) This is a continuation-in-part of application Serial No. 53,361, filed September 1, 1960, now abandoned.

Thisinvention relates to a new and improved zinc alloy and more particularly relates to a new and improved alloy of zinc and a relatively high melting point metal such as Zirconium, titanium, vanadium, chromium, co lumbium, molybdenum, tantalum, tungsten, and uranium. The invention also relates to a master alloy useful in the production of the above zinc base alloy and to a new and improved method for producing such master alloy and final zinc alloy.

In the past, various alloys of zinc and high melting point metals, particularly titanium, have been proposed.

' Generally, these alloys also have contained a small proportion of an easily alloyed metal such as copper. In the preparation of these alloys, it was customary to first prepare a master or intermediate alloy by casting a slab of the master-alloy and crushing the slab to form material of a size which could be conveniently introduced into a bath of molten zinc in order to make the final alloy.

One of the problems in producing alloys by the above method was that the alloys generally were heterogeneous in character with large segregated areas or agglomerates in the zinc matrix of the higher melting point metal and/ or various intermetallic compounds formed between the higher melting point metal and the zinc. These diffi-, culties to a large extent were due to the fact that the high melting point metal generally had a melting point above the boiling point of the zinc.

The alloys were of limited usefulness since they did not possess the desired combination of physical properties such as high strength, ductility, creep resistance and the like. Although some of the deficiencies of the alloys could be corrected to a degree by employing special rolling and annealing procedures and/or by careful control of the processing steps, these techniques were not considered to be a complete solution to the problem.

In view of the above deficiencies and shortcomings, it Was completely unexpected and surprising to discover a new and improved method for producing a novel alloy of zinc and a high melting point metal which not only overcomes the above deficiencies, but also provides advantages and benefits heretofore unattainable. For example, since the method of the invention results in the production of a homogeneous zinc base alloy, greater flexibility and simplification of the production operations is possible. Further, the alloy of the invention requires smaller amounts of the alloying components to achieve equivalent physical properties which also simplifies the alloying operation. As a result, savings in material and production costs are affected.

In accordance with the present invention, a new and improved homogeneous zinc base alloy with at least one high melting point metal comprises a substantially uniform, fine particle dispersion of a high melting point metal in a zinc matrix. This alloy is produced by introducing into a zinc melt, a master alloy comprising a substantially uniform, fine particle dispersion of a high melting point metal in a zinc matrix, maintaining the mixture of the molten Zinc and the master alloy at an elevated temperature untilthe master alloy is substantially completely dispersed in the molten zinc and then cooling the melt to solidify it and produce the substantially uniform, fine particle dispersion of the high melting point metal in the zinc matrix.

The master alloy employed is produced by introducing into a zinc melt a greater percentage of the high melting point metal than is desired in the final alloy, then substantially uniformly dispersing the high melting point metal in the molten zinc and rapidly cooling the resulting melt to form a homogeneous master alloy in which the high melting point metal is a substantially uniform dispersion of fine particle size in a zinc matrix.

The high melting point metal alloyed with the zinc in accordance with the invention generally has a melting point above the boiling point of the zinc, that is, above about 900 C. Suitable high melting point metals include zirconium, titanium, vanadium, chromium, columbium, molybdenum, tantalum, tungsten, uranium and the like. Of the materials mentioned, tungsten has one of the highest melting points, in the range of about 3400 C. The high melting point metal may be introduced into the zinc melt to form the master alloy in any suitable form such as chunks, rods and the like. the size of the high melting point metal incorporated into the melt is relatively small to facilitate rapid dispersion of the metal in the molten zinc. Preferably, the proportion of the high melting point metal in the master alloy is less than about 5% by weight.

In the production of both the master alloy and the final alloy product, it is desirable to employ zinc of high purity, that is, in the range of about 99.9% purity. Zinc of this purity is soft and ductile and recrystallizes at a low temperature.

In the formation of the master alloy, the pure zinc is heated, preferably in an induction furnace, to a temperature above the melting point thereof, namely, above 420 C. Thereafter, while the melt is maintained above its melting point and below about its boiling point (900 C.), the high melting point metal is introduced into the melt. Preferably, the temperature of the molten Zinc during the incorporation of the metal, is maintained above the liquidus point of the highest melting intermetallic constituents (peritectics) formed in the alloying operation while still maintaining the melt below the boiling point of the zinc. Advantageously, the temperature of the melt is maintained in the range of about 650 to 815 C.

As mentioned above, the melt is maintained at the elevated temperature until the high melting point metal is uniformly dispersed or dissolved in the melt. If desired, the melting and alloying operations may be conducted under a flux blanket although this is not essential.

After the high melting point metal is substantially uniformly dispersed in the molten zinc, solidification of the melt may be effected. In accordance with the invention, this is accomplished by uniformly and rapidly cooling the melt. Advantageously, the molten alloy is subdivided into relatively small masses which can be cooled quickly by water or another cooling medium. For example, the molten master alloy may be poured through a sieve-like device to break the melt into relatively small droplets or masses which are then caused to fall into a tank of cold water. Advantageously, the cooling water is circulated to keep temperature variations of the water at a minimum. Because of the relatively small mass of each alloy drop let and the great temperature difference between the droplet and the cooling water, heat is rapidly extracted from the droplet and the high melting point metal is crystallized as a substantially uniform dispersion of very fine particles throughout a zinc matrix. The solidified droplets or nodules are separated from the water and dried prior to use in the production of final alloy products.

The formation of the final alloy product is similar to that of the master alloy except that the alloying con- Advantageously,

stituent incorporated in the molten zinc is the master alloy rather than the high melting point metal. Pure zinc is melted and advantageously maintained at a temperature slightly above the melting point of the zinc, e.g., about 480 to 540 C., and the small master alloy only very small amounts of copper in the range of about 0.15% or 0.2% to 0.5% by weight and titanium in the range of about 0.06% to 0.3% or 0.35% to produce alloys having outstanding physical properties. If desired, larger amounts of copper up to about 2% and titanium up to masses are introduced into the molten zinc. Other alloy- 5 about 0.5% may be used provided the method of the ing ingredients, for example, copper, also may be introinvention is employed in the production of such alloys. duced into the molten zinc, if desired, either in the form The following table shows the phys1cal properties of of the pure metal or as a master alloy. typical alloys of the 1nvent1on. In the table, Tlnckness After the master alloy has been substantially comis the gage thickness given in lnches; Hardness 1s elther pletely dispersed within the molten zinc to form a 10 Scleroscope hardness or Rockwell hardness on the 1ST homogeneous melt, the molten alloy is cooled to solidify scale as designated; Dynamic Dllciiliry 1s e n 1n n the alloy. Advantageously, this solidification again may Uliimate Tensile Strength 1s glven both longitudinal or be accomplished through the use of a cooling medium parallel to the dlrectlon of rolling, and transverse or persuch as water. Preferably, the proportion of the cooling pcndlcular to the dlrectlon of rolllng in pounds per square medium to the quantity of the molten alloy is sufficiently 5 1nch; Yield Slrengt/z 1s given 1n the same manner, and large that substantially instantaneous solidification takes Per ent Elongation expressed in percentages 1n 2 inches place so that the high melting point metal is solidified 1S given In the Same manner N0 heat treatment Was P within the zinc matrix as very fine, uniformly dispersed formed subsequent to rolllng for any of the alloys llsted.

TABLE 1 l 1 Chemical Analysis, l lltiniatc Tensile Yield Strength 3 Elongation Wt. Percent I i Strength 2 (psi) (p.s.i.) (Percent 111 2 111.) Alloy No. (Balance Zinc) Thickness Hardness 1 Dynamic 1 7 (inches) Ductlhty (inches) Cu Ti Long Trans. Long Trans Long. Trans.

1 0. 31 0.105 0, 140 20.100 37,800 10, 200 21, 300 38.0 21.2" 2 0.255 0.113 0. 0140 27,100 30, 750 17.300 1s, 800 20.5 18.5 3 0.24 0.114 0.0140 20,300 37,900 17,500 0, 200 31.25 20.0 4 0.27 0.130 0.0120 7,300 39, 950 17, 600 22,450 33. 25 26.7 5 0.19 0,205 0,115 25, 000 20,950 18, 250 18,400 27.0 10.0 0 0.215 0. 215 0. 017 .50, 050 41,250 20,150 0,100 15.5 16.8 7 0.25 0.23 0.0145 28,590 35, 000 18, 580 22,500 14.0 4.75 s 0.25 0.27 0.0107 8, 870 as, 720 17,160 24,080 13.9 8.6 9 0.27 0, 29 0. 0155 27, 550 30,190 17, 290 22.800 28.0 11.0 10.. 0. 25 1 0.30 1 0. 0170 7,700 37,230 17,440 23,140 11.0 9.5

l Alloy Nos. 1 through 4 Sclcroscopc: Nos. 5 through 10 Rockwell 1ST Scale.

2 Strain rate of 0.11 inch per inch after yield point.

3 0.2% otisetstrain rate of 0.014 inch per inch per minute. particles either of the metal or intermetallic compounds with zinc. Continuous casting apparatus provide a convenient means for rapidly cooling the molten alloy.

The novel homogeneous zinc base alloy produced in accordance with the invention possesses a number of unique physical characteristics because of the substantially uniform dispersion of the high melting point metal as very small particles within the zinc matrix. Since the particles of the high melting point metal are extremely small in size, the number of particles dispersed in the zinc matrix is substantially greater than would be the case if larger particle sizes were dispersed therein. As a result, only a minimum amount of the high melting point metal is required to achieve improved physical properties in the alloy. Also, because only a minimum amount of the high melting point metal achieves the desired high level of physical properties, the alloying of the high melting point metal in the zinc is much simpler than if larger amounts of the high melting point metal were required since as the proportion of the high melting point metal increases, it becomes more difficult to'alloy the metal with zinc.

The improved physical characteristics of alloys produced in accordance with the invention are readily apparent in alloys in which titanium and copper are combined with the zinc. In the past, it was considered essential that several percent of copper be included in the alloy so that suflicient titanium could be alloyed with the zinc to achieve a high level of creep resistance and strength. More recently, it was proposed that titanium could be alloyed with zinc even when smaller amounts of copper were employed in the range of 0.5 to l or 2%. Attempts to reduce the proportion of copper and titanium in the zinc alloy without adversely afiecting physical properties have complicated the problem since it was necessary to use additional other alloying ingredients such as chromium and/or manganese.

In contrast, the alloys of the present invention require The alloys of the present invention are particularly suited for use as lithographic plates because of the uniform, fine particle dispersion of the high melting point metal in the zinc matrix. Since Zinc generally abrades more readily during the graining process leaving the particles of the high melting point metal and/or intermetallic compounds, non-uniformity may result if the particles are large. However, if the high melting point metal and/or the intermetallics are of a very fine particle size as in the alloy of the invention, graining will leave a uniform surface and produce sharp detail in the finished plate.

As shown by the detailed description and specific examples above, the present invention provides a novel alloy composition and a new and improved method for producing this alloy. The composition and method of the invention not only overcome many of the difiiculties of previous alloys and methods heretofore proposed, but also additional benefits and advantages are now attainable. The method of the invention permits simplification and greater flexibility of the alloy production operations. Also, the alloy of the invention possesses high level physical properties even though smaller amounts of the alloying constituents are employed. These advantages permit savings in material and production costs.

It is apparent from the above description of the invention that various modifications in the particular materials and procedures described may be made within the scope of the invention. For example, other means may be employed for rapidly cooling the melt, such as known chill casting methods. Therefore, the invention is not intended to be limited to the specific materials and procedures described in detail herein except as may be required by the following claims.

What is claimed is:

1. In a procedure for making a zinc base master alloy containing at least one high melting point alloying metal selected from the group consisting of zirconium, titanium, vanadium, chromium, columbium, molybdenum, tantalum, tungsten, and uranium, the steps of introducing said high melting point metal into a zinc melt, substantially uniformly dispersing said high melting point metal in said melt, and rapidly cooling the resulting melt to form a substantially homogeneous master alloy having a substantially uniform, fine particle dispersion of said high melting point metal in a zinc matrix.

2. In a procedure for making a zinc base alloy containing at least one high melting point alloying metal selected from the group consisting of zirconium, titanium, vanadium, chromium, columbium, molybdenum, tantalum, tungsten, and uranium, the steps of introducing into a zinc melt, a substantially homogeneous master alloy having a substantially uniform, fine particle dispersion of said high melting point metal, maintaining said melt at an elevated temperature until the master alloy is substantially uniformly dispersed in said melt, and rapidly cooling said melt to produce a substantially homogeneous zinc base alloy having a substantially uniform, fine particle dispersion of said high melting point metal in a zinc matrix.

3. A homogeneous, fine grain size, zinc base master alloy consisting essentially of a substantially uniform dispersion of a high melting point metal of fine particle size In a zinc matrix, said high melting point metal being selected from the group consisting of zirconium, titanium, vanadium, chromium, columbium, molybdenum, tantalum, tungsten, and uranium.

4. A fine grain size, zinc base alloy consisting essentially of a substantially uniform dispersion of a high melting point metal of fine particle size in a zinc matrix, said high melting point metal being selected from the group consisting of zirconium, titanium, vanadium, chromium, columbium, molybdenum, tantalum, tungsten, and uranium and comprising about 0.06% to 0.3% by Weight of said alloy.

5. A homogeneous, fine grain size, zinc base alloy comprising a substantially uniform dispersion of copper and titanium of fine particle size in a zinc matrix, said copper and said titanium comprising about 0.2% to 0.8% by Weight of said alloy.

6. In a procedure for making a zinc base master alloy containing titanium, the steps of introducing a greater percentage of the titanium than desired in the final alloy into a molten zinc melt having a temperature that is below the melting point of the titanium and the boiling point of the zinc and that is above the melting point of the zinc, alloying the titanium in the molten zinc melt While maintaining the melt at a temperature Within the above-specified range and until the titanium is completely mixed with and dispersed through the molten zinc, substantially instantaneously uniformly cooling the master alloy to inhibit grain growth and segregation of the titanium and intermetallics within the master alloy, and controlling the cooling to provide a solidified master alloy of small grain size and improved homogeneity.

7. In a procedure for making a zinc base master alloy having a relatively small grain size and improved homogeneity and which contains titanium, the steps of introducing a greater percentage of the titanium than desired in the final alloy into a molten zinc base metal melt containing about 99.9% zinc and having a temperature about 420 C. to 900 C., alloying the titanium in the molten zinc melt while maintaining the melt at a temperature within the above-specified range and until the titanium is completely mixed with and dispersed through the molten zinc to provide a master alloy, dividing the master alloy into relatively small masses while the zinc is still molten therein, substantially instantaneously chill-casting the divided masses of the master alloy in such a manner as to inhibit grain growth and segregation of the high melting point metal and intermetallics within the master alloy.

8. In a procedure for making a zinc base metal master alloy containing titanium of improved homogeneity and fine grain structure, the steps of dissolving titanium in solid form in a molten zinc base metal melt, maintaining the temperature of the molten zinc melt about 650 C. to 815 C., alloying the titanium in the molten zinc while maintaining the melt within the temperature of the abovespecified range and while the titanium is mixed with and dispersed through the molten zinc to form a master alloy, dividing the master alloy into relatively small masses while the zinc base metal is substantially within the abovespecified temperature range, substantially instantaneously uniformly individually cooling the small masses of the master alloy and chill-casting them to inhibit grain growth and segregation of the titanium and intermetallics within the master alloy.

9. In a procedure for making a zinc base alloy containing titanium, the steps of introducing into a zinc melt a substantially homogeneous master alloy having a substantially uniform, fine particle dispersion of said titanium, maintaining said melt at an elevated temperature of about 480 C. to 540 C. until the master alloy is substantially uniformly dispersed in said melt, and rapidly cooling said melt to produce a substantially homogeneous zinc base alloy having a substantially uniform, fine particle dispersion of said titanium in a zinc matrix.

10. In a procedure for making a zinc base alloy containing titanium and copper, the steps of introducing into a zinc melt a substantially homogeneous master alloy having a substantially uniform, fine particle dispersion of titanium, maintaining said melt at an elevated temperature of about 480 C. to 540 C. until the master alloy is substantially uniformly dispersed in said melt, alloying said metal melt with a small amount of copper, and rapidly cooling said melt to produce a substantially homogeneous zinc base alloy having a substantially uniform, fine particle dispersion of said titanium and copper in a zinc matrix.

11. In a procedure for making a zinc base alloy having relatively fine grain structure with improved homogeneity and which contains about 0.2% to 2.0% copper, from about 0.1% to 0.5% titanium-copper and the balance zinc, and the titanium is principally in the form of 'titanium-zinc intermetallics homogeneously dispersed through the alloy, the steps of introducing into a zinc melt, asubstantially homogeneous master alloy having a substantially uniform, fine particle dispersion of titanium constituting from about 0.5% to 5% by weight of said alloy, maintaining said melt at a temperature of about 480 C. to 540 C. until the master alloy is substantially uniformly dispersed in said melt, alloying the resulting melt With the above-specified amounts of copper, and rapidly cooling said melt to produce a substantially homogeneous zinc base alloy having a substantially uniform, fine particle dispersion of said titanium and copper in a zinc matrix.

12. A homogeneous, fine grain size, zinc base master alloy consisting essentially of a substantially uniform dispersion of titanium of fine particle size in a zinc matrix, said titanium comprising about 0.5% to 5% by weight of said'alloy.

13. A homogeneous, fine grain size, zinc base alloy consisting essentially of a substantially uniform dispersion of copper and a high melting point metal of fine particle size in a zinc matrix, said high melting point metal being selected from a group consisting of zirconium, titanium, vanadium, chromium, columbium, molybdenum, tantalum, tungsten, and uranium, said copper comprising about 0.35% to 2% by weight of said alloy, and said high melting point metal comprising about 0.15% to 0.5% by weight of said alloy.

14. A homogeneous, fine grain size, zinc base alloy consisting essentially of a substantially uniform dispersion of copper and titanium of fine particle size in a zinc matrix, said copper comprising about 0.35% to 2% by weight of said alloy, and said titanium comprising about 0.15% to 0.5% by weight of said alloy.

15. A homogeneous, fine grain size, zinc base alloy consisting essentially of a substantially uniform dispersion of titanium of fine particle size in a zinc matrix, said titanium comprising about 0.15% to 0.5% by Weight of said alloy.

3,2 54,993 7 FOREIGN PATENTS 362,507 12/1931 Great Britain.

References Cited by the Examiner UNITED OTHER REFERENCES STATES PATENTS 5 Zeitschrift fur Anorganische Cherme, vol. 59, 1908, Boyle 75-178 page 427 Holzwarth 7 5-178 P P Q er 75-478 DAVID L. RECK, Primary Examiner. Gluhani 75-178 H London et aL 10 D. L. REISDORI, R. O. DEAN, ASSlS/(Ull Examzners. Zvanut 75178 

2. IN A PROCEDURE FOR MAKING A ZINC BASE ALLOY CONTAINING AT LEAST ONE HIGH MELTING POINT ALLOYING METAL SELECTED FROM THE GROUP CONSISTING OF ZIRCONIUM, TITANIUM, VANADIUM, CHROMIUM, COLUMBIUM, MOLYBDENUM, TANTALUM, TUNGSTEN, AND URANIUM, THE STEPS OF INTRODUCING INTO A ZINC MELT, A SUBSTANTIALLY HOMOGENEOUS MASTER ALLOY HAVING A SUBSTANTIALLY UNIFORM, FINE PARTICLE DISPERSION OF SAID HIGH MELTING POINT METAL, MAINTAINING SAID METL AT AN ELEVATED TEMPERATURE UNTIL THE MASTER ALLOY IS SUBSTANTIALLY UNIFORMLY DISPERSED IN SAID METL, AND RAPIDLY COOLING SAID MELT TO PRODUCE A SUBSTANTIALLY HOMOGENEOUS ZINC BASE ALLOY HAVING A SUBSTANTIALLY UNIFORM, FINE PARTICLE DISPERSION OF SAID HIGH MELTING POINT METAL IN A ZINC MATRIX. 